View Full Version : DNA websites cast broad net for identifying people

June Pelo
15-10-18, 18:15
About 60% of the US population with European heritage may be identified from their DNA by searching consumer websites, even if they've never made their own genetic information available. And that number will grow as more and more people upload their DNA profiles to websites that use genetic analysis to find relatives.

The use of such databases for criminal investigations made headlines in April, when authorities announced they'd used a genetic genealogy website to connect some crime scene DNA to a man they then accused of being the so-called Golden State Killer, a serial rapist and murderer.

In general, such searches begin on a site by finding a relative linked to a DNA sample. Then sleuths can use other information like published family trees, public records and lists of survivors in obituaries, plus whatever they know abut the person whose DNA began the process. They can build their own speculative family trees,. Eventually, they can point to someone whose DNA is then found to match the original sample.

With DNA databases you need just a minute fraction of the population to really identify many more people. Each person in a DNA database acts as a beacon that illuminates hundreds of distant relatives according to Yaniv Erlich of Columbia University. His study focused on Americans of European descent because such people are over-represented in DNA databases which makes it easier to find relatives.

The researchers started with the 1.28 million participants on the My Heritage site at the time they did the work. Most had a northern European genetic background. For each, they looked for relatives more distant than first cousins elsewhere in the database. About 60% of the time, they found someone whose genetic similarity was at least equal to that of a third cousin, similar to the degree of relatedness that led to the Golden State Killer suspect. Third cousins share great-great grandparents.

With some basic assumptions about what kind of data would be available for a criminal suspect, the researchers calculated they could pare down the possible identity of the initial person to just 16 or 17 people. That's limited enough that police could zero in with further investigation.

Erlich and his co-authors suggested that such searches could cast a broader net in the near future. A database with DNA profiles of just 2% of a population is enough to match nearly everybody with somebody who's as closely related as a third cousin. From that, they calculated that the genetic profiles of about 3 million Americans of European descent could deliver the equivalent of a third cousin for more than 90% of that ethnic grouping.

Websites are getting very close to that, according to Erlich. He noted that My Heritage now has more than 1,75 million participants. He said the website does not allow forensic searches. Two DNA experts unconnected to the study said third and fourth cousins can both lead to identifications.

Yaniv Erlich is also chief scientific officer of the My Heritage website.

Malcolm Ritter
AP Science Writer
October 13, 2018